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  <div class="headertitle"><div class="title">bandwidth.cpp</div></div>
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<a href="bandwidth_8cpp.html">Go to the documentation of this file.</a><div class="fragment"><div class="line"><a id="l00001" name="l00001"></a><span class="lineno">    1</span><span class="comment">/* Flow</span></div>
<div class="line"><a id="l00002" name="l00002"></a><span class="lineno">    2</span><span class="comment"> * Copyright 2023 Akamai Technologies, Inc.</span></div>
<div class="line"><a id="l00003" name="l00003"></a><span class="lineno">    3</span><span class="comment"> *</span></div>
<div class="line"><a id="l00004" name="l00004"></a><span class="lineno">    4</span><span class="comment"> * Licensed under the Apache License, Version 2.0 (the</span></div>
<div class="line"><a id="l00005" name="l00005"></a><span class="lineno">    5</span><span class="comment"> * &quot;License&quot;); you may not use this file except in</span></div>
<div class="line"><a id="l00006" name="l00006"></a><span class="lineno">    6</span><span class="comment"> * compliance with the License.  You may obtain a copy</span></div>
<div class="line"><a id="l00007" name="l00007"></a><span class="lineno">    7</span><span class="comment"> * of the License at</span></div>
<div class="line"><a id="l00008" name="l00008"></a><span class="lineno">    8</span><span class="comment"> *</span></div>
<div class="line"><a id="l00009" name="l00009"></a><span class="lineno">    9</span><span class="comment"> *   https://www.apache.org/licenses/LICENSE-2.0</span></div>
<div class="line"><a id="l00010" name="l00010"></a><span class="lineno">   10</span><span class="comment"> *</span></div>
<div class="line"><a id="l00011" name="l00011"></a><span class="lineno">   11</span><span class="comment"> * Unless required by applicable law or agreed to in</span></div>
<div class="line"><a id="l00012" name="l00012"></a><span class="lineno">   12</span><span class="comment"> * writing, software distributed under the License is</span></div>
<div class="line"><a id="l00013" name="l00013"></a><span class="lineno">   13</span><span class="comment"> * distributed on an &quot;AS IS&quot; BASIS, WITHOUT WARRANTIES OR</span></div>
<div class="line"><a id="l00014" name="l00014"></a><span class="lineno">   14</span><span class="comment"> * CONDITIONS OF ANY KIND, either express or implied.</span></div>
<div class="line"><a id="l00015" name="l00015"></a><span class="lineno">   15</span><span class="comment"> * See the License for the specific language governing</span></div>
<div class="line"><a id="l00016" name="l00016"></a><span class="lineno">   16</span><span class="comment"> * permissions and limitations under the License. */</span></div>
<div class="line"><a id="l00017" name="l00017"></a><span class="lineno">   17</span><span class="comment"></span> </div>
<div class="line"><a id="l00018" name="l00018"></a><span class="lineno">   18</span><span class="comment">/// @file</span></div>
<div class="line"><a id="l00019" name="l00019"></a><span class="lineno">   19</span><span class="comment"></span><span class="preprocessor">#include &quot;<a class="code" href="bandwidth_8hpp.html">flow/net_flow/detail/stats/bandwidth.hpp</a>&quot;</span></div>
<div class="line"><a id="l00020" name="l00020"></a><span class="lineno">   20</span><span class="preprocessor">#include &quot;<a class="code" href="util_2util_8hpp.html">flow/util/util.hpp</a>&quot;</span></div>
<div class="line"><a id="l00021" name="l00021"></a><span class="lineno">   21</span> </div>
<div class="line"><a id="l00022" name="l00022"></a><span class="lineno">   22</span><span class="keyword">namespace </span><a class="code hl_namespace" href="namespaceflow_1_1net__flow.html">flow::net_flow</a></div>
<div class="line"><a id="l00023" name="l00023"></a><span class="lineno">   23</span>{</div>
<div class="line"><a id="l00024" name="l00024"></a><span class="lineno">   24</span><span class="comment">// Implementations.</span></div>
<div class="line"><a id="l00025" name="l00025"></a><span class="lineno">   25</span> </div>
<div class="line"><a id="l00026" name="l00026"></a><span class="lineno"><a class="line" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#ad2432d0e20ebfd1b95009e10f10f08be">   26</a></span><a class="code hl_function" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#ad2432d0e20ebfd1b95009e10f10f08be">Send_bandwidth_estimator::Send_bandwidth_estimator</a>(<a class="code hl_class" href="classflow_1_1log_1_1Logger.html">log::Logger</a>* logger_ptr, <a class="code hl_typedef" href="classflow_1_1util_1_1Shared__ptr__alias__holder.html#aef7998db71c60eeb5d1e3d1a97c14886">Peer_socket::Const_ptr</a> sock) :</div>
<div class="line"><a id="l00027" name="l00027"></a><span class="lineno">   27</span>  Log_context(logger_ptr, <a class="code hl_enumeration" href="namespaceflow.html#a3938730ab4b89daf13d027a5f620e7ce">Flow_log_component</a>::S_NET_FLOW),</div>
<div class="line"><a id="l00028" name="l00028"></a><span class="lineno">   28</span>  m_sock(sock), <span class="comment">// Get a weak_ptr from a shared_ptr.</span></div>
<div class="line"><a id="l00029" name="l00029"></a><span class="lineno">   29</span>  m_bytes_per_time_smoothed(0), <span class="comment">// Just to get the advertised answer in bandwidth_estimate_per_time() immediately.</span></div>
<div class="line"><a id="l00030" name="l00030"></a><span class="lineno">   30</span>  m_bytes_per_time_less_smoothed(0), <span class="comment">// For cleanliness.</span></div>
<div class="line"><a id="l00031" name="l00031"></a><span class="lineno">   31</span>  m_bytes_this_sample(0), <span class="comment">// on_acks() does assume this is already zero before it is first called.</span></div>
<div class="line"><a id="l00032" name="l00032"></a><span class="lineno">   32</span>  m_no_acks_yet(true), <span class="comment">// As documented.</span></div>
<div class="line"><a id="l00033" name="l00033"></a><span class="lineno">   33</span>  m_no_samples_yet(true) <span class="comment">// As documented.</span></div>
<div class="line"><a id="l00034" name="l00034"></a><span class="lineno">   34</span>{</div>
<div class="line"><a id="l00035" name="l00035"></a><span class="lineno">   35</span>  <span class="comment">// Nothing.</span></div>
<div class="line"><a id="l00036" name="l00036"></a><span class="lineno">   36</span>}</div>
<div class="line"><a id="l00037" name="l00037"></a><span class="lineno">   37</span> </div>
<div class="line"><a id="l00038" name="l00038"></a><span class="lineno"><a class="line" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a135f0a46b34063e10abfb16de057cbb3">   38</a></span><a class="code hl_typedef" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a40993b2699c5e8ab69dfd56e57ecdd28">Send_bandwidth_estimator::n_bytes_t</a> <a class="code hl_function" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a135f0a46b34063e10abfb16de057cbb3">Send_bandwidth_estimator::bandwidth_bytes_per_time</a>()<span class="keyword"> const</span></div>
<div class="line"><a id="l00039" name="l00039"></a><span class="lineno">   39</span><span class="keyword"></span>{</div>
<div class="line"><a id="l00040" name="l00040"></a><span class="lineno">   40</span>  <span class="keywordflow">return</span> <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#aee344345b4b4c54a0854bfd23817ef46">m_bytes_per_time_smoothed</a>;</div>
<div class="line"><a id="l00041" name="l00041"></a><span class="lineno">   41</span>}</div>
<div class="line"><a id="l00042" name="l00042"></a><span class="lineno">   42</span> </div>
<div class="line"><a id="l00043" name="l00043"></a><span class="lineno"><a class="line" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#afe271b3d4c8cb73d06048a41871c795e">   43</a></span><span class="keywordtype">void</span> <a class="code hl_function" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#afe271b3d4c8cb73d06048a41871c795e">Send_bandwidth_estimator::on_acks</a>(<span class="keywordtype">size_t</span> bytes)</div>
<div class="line"><a id="l00044" name="l00044"></a><span class="lineno">   44</span>{</div>
<div class="line"><a id="l00045" name="l00045"></a><span class="lineno">   45</span>  <span class="keyword">using </span>boost::chrono::microseconds;</div>
<div class="line"><a id="l00046" name="l00046"></a><span class="lineno">   46</span>  <span class="keyword">using </span>boost::chrono::round;</div>
<div class="line"><a id="l00047" name="l00047"></a><span class="lineno">   47</span>  <span class="keyword">using </span>boost::chrono::ceil;</div>
<div class="line"><a id="l00048" name="l00048"></a><span class="lineno">   48</span>  <span class="keyword">using </span>std::max;</div>
<div class="line"><a id="l00049" name="l00049"></a><span class="lineno">   49</span> </div>
<div class="line"><a id="l00050" name="l00050"></a><span class="lineno">   50</span>  <span class="comment">/* Received &quot;bytes&quot; bytes of clean acknowledgment(s).  Assuming both user and Node are sending</span></div>
<div class="line"><a id="l00051" name="l00051"></a><span class="lineno">   51</span><span class="comment">   * data at the maximum possible rate, try to estimate the bandwidth as the rate of sending.  Keep</span></div>
<div class="line"><a id="l00052" name="l00052"></a><span class="lineno">   52</span><span class="comment">   * passing the bandwidth measurements into a pair of filters to get the result.  Each sample is an</span></div>
<div class="line"><a id="l00053" name="l00053"></a><span class="lineno">   53</span><span class="comment">   * accumulation of acked bytes over the time period &gt; SRTT.</span></div>
<div class="line"><a id="l00054" name="l00054"></a><span class="lineno">   54</span><span class="comment">   *</span></div>
<div class="line"><a id="l00055" name="l00055"></a><span class="lineno">   55</span><span class="comment">   * This implementation is a reasonably informed rip-off of tcp_westwood.c from the Linux kernel.</span></div>
<div class="line"><a id="l00056" name="l00056"></a><span class="lineno">   56</span><span class="comment">   * That implementation is by the creators of the Westwood+ algorithm, so it&#39;s probably</span></div>
<div class="line"><a id="l00057" name="l00057"></a><span class="lineno">   57</span><span class="comment">   * trustworthy (also we have tested it).</span></div>
<div class="line"><a id="l00058" name="l00058"></a><span class="lineno">   58</span><span class="comment">   *</span></div>
<div class="line"><a id="l00059" name="l00059"></a><span class="lineno">   59</span><span class="comment">   * The basic pattern is:</span></div>
<div class="line"><a id="l00060" name="l00060"></a><span class="lineno">   60</span><span class="comment">   *</span></div>
<div class="line"><a id="l00061" name="l00061"></a><span class="lineno">   61</span><span class="comment">   *   - on_acks(N) called the first time:</span></div>
<div class="line"><a id="l00062" name="l00062"></a><span class="lineno">   62</span><span class="comment">   *     - m_bytes_this_sample = 0; // True after construction.</span></div>
<div class="line"><a id="l00063" name="l00063"></a><span class="lineno">   63</span><span class="comment">   *     - m_this_sample_start_time = now();</span></div>
<div class="line"><a id="l00064" name="l00064"></a><span class="lineno">   64</span><span class="comment">   *     - m_bytes_this_sample += N; // Equivalent to m_bytes_this_sample = N;</span></div>
<div class="line"><a id="l00065" name="l00065"></a><span class="lineno">   65</span><span class="comment">   *   - ...Time passes....</span></div>
<div class="line"><a id="l00066" name="l00066"></a><span class="lineno">   66</span><span class="comment">   *   - on_acks(N) called subsequently:</span></div>
<div class="line"><a id="l00067" name="l00067"></a><span class="lineno">   67</span><span class="comment">   *     - since_sample_start = now() - m_this_sample_start_time;</span></div>
<div class="line"><a id="l00068" name="l00068"></a><span class="lineno">   68</span><span class="comment">   *     - if (since_sample_start &gt; SRTT):</span></div>
<div class="line"><a id="l00069" name="l00069"></a><span class="lineno">   69</span><span class="comment">   *       - // Sample is long enough; update bandwidth estimate; start new sample.</span></div>
<div class="line"><a id="l00070" name="l00070"></a><span class="lineno">   70</span><span class="comment">   *       - bytes_per_time_this_sample = m_bytes_this_sample / since_sample_start</span></div>
<div class="line"><a id="l00071" name="l00071"></a><span class="lineno">   71</span><span class="comment">   *       - m_bytes_per_time_smoothed = filtered mix of m_bytes_per_time_smoothed and</span></div>
<div class="line"><a id="l00072" name="l00072"></a><span class="lineno">   72</span><span class="comment">   *         bytes_per_time_this_sample;</span></div>
<div class="line"><a id="l00073" name="l00073"></a><span class="lineno">   73</span><span class="comment">   *       - m_bytes_this_sample = 0; m_this_sample_start_time = now();</span></div>
<div class="line"><a id="l00074" name="l00074"></a><span class="lineno">   74</span><span class="comment">   *     - else:</span></div>
<div class="line"><a id="l00075" name="l00075"></a><span class="lineno">   75</span><span class="comment">   *       - // Sample not long enough.  Can&#39;t update bandwidth estimate yet.</span></div>
<div class="line"><a id="l00076" name="l00076"></a><span class="lineno">   76</span><span class="comment">   *     - m_bytes_this_sample += N;</span></div>
<div class="line"><a id="l00077" name="l00077"></a><span class="lineno">   77</span><span class="comment">   *   - ...Time passes....</span></div>
<div class="line"><a id="l00078" name="l00078"></a><span class="lineno">   78</span><span class="comment">   *   - on_acks(N) called subsequently (see above).</span></div>
<div class="line"><a id="l00079" name="l00079"></a><span class="lineno">   79</span><span class="comment">   *   - Etc.</span></div>
<div class="line"><a id="l00080" name="l00080"></a><span class="lineno">   80</span><span class="comment">   *</span></div>
<div class="line"><a id="l00081" name="l00081"></a><span class="lineno">   81</span><span class="comment">   * Some interesting observations about this:</span></div>
<div class="line"><a id="l00082" name="l00082"></a><span class="lineno">   82</span><span class="comment">   *</span></div>
<div class="line"><a id="l00083" name="l00083"></a><span class="lineno">   83</span><span class="comment">   * Note that m_bytes_this_sample is incremented AFTER the bandwidth estimation is recomputed (if</span></div>
<div class="line"><a id="l00084" name="l00084"></a><span class="lineno">   84</span><span class="comment">   * it is recomputed).  So the B/W computation does not include the newest acked data; the newest</span></div>
<div class="line"><a id="l00085" name="l00085"></a><span class="lineno">   85</span><span class="comment">   * acked data instead counts in the NEXT sample.  I am not exactly sure why they did it this way</span></div>
<div class="line"><a id="l00086" name="l00086"></a><span class="lineno">   86</span><span class="comment">   * and not in the opposite (&quot;greedier&quot;) order, but it doesn&#39;t seem like it&#39;s worse.</span></div>
<div class="line"><a id="l00087" name="l00087"></a><span class="lineno">   87</span><span class="comment">   *</span></div>
<div class="line"><a id="l00088" name="l00088"></a><span class="lineno">   88</span><span class="comment">   * The start of the pattern has some subtlety to it.  m_bytes_this_sample and</span></div>
<div class="line"><a id="l00089" name="l00089"></a><span class="lineno">   89</span><span class="comment">   * m_this_sample_start_time are initialized to zero, as seems reasonable: we don&#39;t try to set</span></div>
<div class="line"><a id="l00090" name="l00090"></a><span class="lineno">   90</span><span class="comment">   * m_this_sample_start_time at construction or something, as that can be a long time ago and</span></div>
<div class="line"><a id="l00091" name="l00091"></a><span class="lineno">   91</span><span class="comment">   * bogus.  (tcp_westwood.c agrees with this.  Things are initialized in the .init callback, which</span></div>
<div class="line"><a id="l00092" name="l00092"></a><span class="lineno">   92</span><span class="comment">   * is called upon first TCP ACK receipt, not earlier during connection setup.)  Then</span></div>
<div class="line"><a id="l00093" name="l00093"></a><span class="lineno">   93</span><span class="comment">   * m_bytes_this_sample is incremented by N to N (0 + N == N).  The weird thing is that</span></div>
<div class="line"><a id="l00094" name="l00094"></a><span class="lineno">   94</span><span class="comment">   * tcp_westwood.c for some reason forces this increment in the first on_acks() equivalent to be 0.</span></div>
<div class="line"><a id="l00095" name="l00095"></a><span class="lineno">   95</span><span class="comment">   * If one traces the code, if (first_ack) they set &quot;w-&gt;snd_una = tcp_sk(sk)-&gt;snd_una;&quot;, the</span></div>
<div class="line"><a id="l00096" name="l00096"></a><span class="lineno">   96</span><span class="comment">   * following if () probably does not trigger, and then the likeliest caller of that function</span></div>
<div class="line"><a id="l00097" name="l00097"></a><span class="lineno">   97</span><span class="comment">   * (westwood_fast_bw()) executes &quot;w-&gt;bk += tp-&gt;snd_una - w-&gt;snd_una;&quot;, which increments w-&gt;bk by</span></div>
<div class="line"><a id="l00098" name="l00098"></a><span class="lineno">   98</span><span class="comment">   * 0.  w-&gt;bk is the exact equivalent of our m_bytes_this_sample.</span></div>
<div class="line"><a id="l00099" name="l00099"></a><span class="lineno">   99</span><span class="comment">   *</span></div>
<div class="line"><a id="l00100" name="l00100"></a><span class="lineno">  100</span><span class="comment">   * The comments in tcp_westwood.c about why the snd_una assignment happens there are not entirely</span></div>
<div class="line"><a id="l00101" name="l00101"></a><span class="lineno">  101</span><span class="comment">   * clear to me.  I think basically tp-&gt;snd_una may be incorrect for some reason (?) at connection</span></div>
<div class="line"><a id="l00102" name="l00102"></a><span class="lineno">  102</span><span class="comment">   * open, though I don&#39;t know why, so they just force the first part of the sample to be 0.  I am</span></div>
<div class="line"><a id="l00103" name="l00103"></a><span class="lineno">  103</span><span class="comment">   * not really sure.  I have chosen to deviate slightly and in fact perform that first increment.</span></div>
<div class="line"><a id="l00104" name="l00104"></a><span class="lineno">  104</span><span class="comment">   * Since it&#39;s just the first measurement, it is very very unlikely to matter, so I chose</span></div>
<div class="line"><a id="l00105" name="l00105"></a><span class="lineno">  105</span><span class="comment">   * simplicity... the &quot;bytes&quot; argument for us is given directly (no need to perform snd_una math),</span></div>
<div class="line"><a id="l00106" name="l00106"></a><span class="lineno">  106</span><span class="comment">   * and we have no reason to distrust it. */</span></div>
<div class="line"><a id="l00107" name="l00107"></a><span class="lineno">  107</span> </div>
<div class="line"><a id="l00108" name="l00108"></a><span class="lineno">  108</span>  <span class="keyword">const</span> <a class="code hl_typedef" href="classflow_1_1util_1_1Shared__ptr__alias__holder.html#aef7998db71c60eeb5d1e3d1a97c14886">Peer_socket::Const_ptr</a> sock = <a class="code hl_function" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a8676142f693c447be89b667403fecea1">socket</a>();</div>
<div class="line"><a id="l00109" name="l00109"></a><span class="lineno">  109</span> </div>
<div class="line"><a id="l00110" name="l00110"></a><span class="lineno">  110</span>  <span class="keywordflow">if</span> (<a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#adc8e7ca2c14f74a85beb863c145b97ba">m_no_acks_yet</a>)</div>
<div class="line"><a id="l00111" name="l00111"></a><span class="lineno">  111</span>  {</div>
<div class="line"><a id="l00112" name="l00112"></a><span class="lineno">  112</span>    <span class="comment">// First on_acks() call (first acked bytes).  Begin first sample by marking the time.</span></div>
<div class="line"><a id="l00113" name="l00113"></a><span class="lineno">  113</span> </div>
<div class="line"><a id="l00114" name="l00114"></a><span class="lineno">  114</span>    <a class="code hl_define" href="log_8hpp.html#affcf2e4c496ce3f42adf981669c623b8">FLOW_LOG_TRACE</a>(<span class="stringliteral">&quot;bw_est [&quot;</span> &lt;&lt; sock &lt;&lt; <span class="stringliteral">&quot;] update: start first sample at 0 bytes.&quot;</span>);</div>
<div class="line"><a id="l00115" name="l00115"></a><span class="lineno">  115</span> </div>
<div class="line"><a id="l00116" name="l00116"></a><span class="lineno">  116</span>    <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#adc8e7ca2c14f74a85beb863c145b97ba">m_no_acks_yet</a> = <span class="keyword">false</span>;</div>
<div class="line"><a id="l00117" name="l00117"></a><span class="lineno">  117</span>    <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#ac627f8c9ae6c51c2ea14dd46af4f4150">m_this_sample_start_time</a> = Fine_clock::now();</div>
<div class="line"><a id="l00118" name="l00118"></a><span class="lineno">  118</span>  }</div>
<div class="line"><a id="l00119" name="l00119"></a><span class="lineno">  119</span>  <span class="keywordflow">else</span> <span class="comment">// if (2nd on_acks() and later)</span></div>
<div class="line"><a id="l00120" name="l00120"></a><span class="lineno">  120</span>  {</div>
<div class="line"><a id="l00121" name="l00121"></a><span class="lineno">  121</span>    <span class="comment">/* Standard on_acks() call.  Some acks were just received from the other side.  See if enough</span></div>
<div class="line"><a id="l00122" name="l00122"></a><span class="lineno">  122</span><span class="comment">     * time has passed since the sample was first started.  &quot;Enough time&quot; is defined as at least</span></div>
<div class="line"><a id="l00123" name="l00123"></a><span class="lineno">  123</span><span class="comment">     * SRTT (which is the estimate for the round trip time maintained elsewhere by measuring how</span></div>
<div class="line"><a id="l00124" name="l00124"></a><span class="lineno">  124</span><span class="comment">     * quickly packets are acked). */</span></div>
<div class="line"><a id="l00125" name="l00125"></a><span class="lineno">  125</span> </div>
<div class="line"><a id="l00126" name="l00126"></a><span class="lineno">  126</span>    <span class="keyword">const</span> <a class="code hl_typedef" href="namespaceflow.html#a48799f1263cdeedec125be51a3db2b79">Fine_duration</a> since_sample_start = Fine_clock::now() - <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#ac627f8c9ae6c51c2ea14dd46af4f4150">m_this_sample_start_time</a>;</div>
<div class="line"><a id="l00127" name="l00127"></a><span class="lineno">  127</span>    assert(since_sample_start.count() &gt;= 0);</div>
<div class="line"><a id="l00128" name="l00128"></a><span class="lineno">  128</span> </div>
<div class="line"><a id="l00129" name="l00129"></a><span class="lineno">  129</span>    <span class="keyword">const</span> <a class="code hl_typedef" href="namespaceflow.html#a48799f1263cdeedec125be51a3db2b79">Fine_duration</a>&amp; srtt = sock-&gt;m_snd_smoothed_round_trip_time;</div>
<div class="line"><a id="l00130" name="l00130"></a><span class="lineno">  130</span> </div>
<div class="line"><a id="l00131" name="l00131"></a><span class="lineno">  131</span>    <span class="keywordflow">if</span> (srtt == Fine_duration::zero())</div>
<div class="line"><a id="l00132" name="l00132"></a><span class="lineno">  132</span>    {</div>
<div class="line"><a id="l00133" name="l00133"></a><span class="lineno">  133</span>      <span class="comment">/* A documented on_acks() requirement is that the bytes that were acked have already</span></div>
<div class="line"><a id="l00134" name="l00134"></a><span class="lineno">  134</span><span class="comment">       * affected SRTT.  Therefore srtt should not be zero.  We needn&#39;t overreact by assert()ing</span></div>
<div class="line"><a id="l00135" name="l00135"></a><span class="lineno">  135</span><span class="comment">       * though -- let&#39;s just keep building the sample then.... */</span></div>
<div class="line"><a id="l00136" name="l00136"></a><span class="lineno">  136</span> </div>
<div class="line"><a id="l00137" name="l00137"></a><span class="lineno">  137</span>      <a class="code hl_define" href="log_8hpp.html#a626c7dc4d3b4dc0b32a8aac8624d66bc">FLOW_LOG_WARNING</a>(<span class="stringliteral">&quot;bw_est [&quot;</span> &lt;&lt; sock &lt;&lt; <span class="stringliteral">&quot;] update: received acks but have no SRTT yet!  This may be &quot;</span></div>
<div class="line"><a id="l00138" name="l00138"></a><span class="lineno">  138</span>                       <span class="stringliteral">&quot;a bug.  Adding [&quot;</span> &lt;&lt; sock-&gt;bytes_blocks_str(bytes) &lt;&lt; <span class="stringliteral">&quot;] to current sample &quot;</span></div>
<div class="line"><a id="l00139" name="l00139"></a><span class="lineno">  139</span>                       <span class="stringliteral">&quot;of [&quot;</span> &lt;&lt; sock-&gt;bytes_blocks_str(<span class="keywordtype">size_t</span>(<a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a0bf439f5cfe98fb1d4d6d55ae605d278">m_bytes_this_sample</a>)) &lt;&lt; <span class="stringliteral">&quot;] bytes &quot;</span></div>
<div class="line"><a id="l00140" name="l00140"></a><span class="lineno">  140</span>                       <span class="stringliteral">&quot;started [&quot;</span> &lt;&lt; since_sample_start &lt;&lt; <span class="stringliteral">&quot;] ago.&quot;</span>);</div>
<div class="line"><a id="l00141" name="l00141"></a><span class="lineno">  141</span>    }</div>
<div class="line"><a id="l00142" name="l00142"></a><span class="lineno">  142</span>    <span class="keywordflow">else</span> <span class="comment">// if (srtt is valid)</span></div>
<div class="line"><a id="l00143" name="l00143"></a><span class="lineno">  143</span>    {</div>
<div class="line"><a id="l00144" name="l00144"></a><span class="lineno">  144</span>      <span class="comment">/* As in tcp_westwood.cpp, if the SRTT is quite small (as in LAN), bandwidth calculations</span></div>
<div class="line"><a id="l00145" name="l00145"></a><span class="lineno">  145</span><span class="comment">       * may get crazy; so put a floor on the sample length, as specified in this socket option. */</span></div>
<div class="line"><a id="l00146" name="l00146"></a><span class="lineno">  146</span>      <span class="keyword">const</span> <a class="code hl_typedef" href="namespaceflow.html#a48799f1263cdeedec125be51a3db2b79">Fine_duration</a> sample_period_floor = sock-&gt;opt(sock-&gt;m_opts.m_st_snd_bandwidth_est_sample_period_floor);</div>
<div class="line"><a id="l00147" name="l00147"></a><span class="lineno">  147</span>      <span class="keyword">const</span> <a class="code hl_typedef" href="namespaceflow.html#a48799f1263cdeedec125be51a3db2b79">Fine_duration</a> min_sample_period = max(srtt, sample_period_floor);</div>
<div class="line"><a id="l00148" name="l00148"></a><span class="lineno">  148</span> </div>
<div class="line"><a id="l00149" name="l00149"></a><span class="lineno">  149</span>      <a class="code hl_define" href="log_8hpp.html#affcf2e4c496ce3f42adf981669c623b8">FLOW_LOG_TRACE</a>(<span class="stringliteral">&quot;bw_est [&quot;</span> &lt;&lt; sock &lt;&lt; <span class="stringliteral">&quot;] update: received acks; current sample &quot;</span></div>
<div class="line"><a id="l00150" name="l00150"></a><span class="lineno">  150</span>                     <span class="stringliteral">&quot;total [&quot;</span> &lt;&lt; sock-&gt;bytes_blocks_str(<span class="keywordtype">size_t</span>(<a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a0bf439f5cfe98fb1d4d6d55ae605d278">m_bytes_this_sample</a>)) &lt;&lt; <span class="stringliteral">&quot;]; &quot;</span></div>
<div class="line"><a id="l00151" name="l00151"></a><span class="lineno">  151</span>                     <span class="stringliteral">&quot;started [&quot;</span> &lt;&lt; round&lt;microseconds&gt;(since_sample_start) &lt;&lt; <span class="stringliteral">&quot;] ago; &quot;</span></div>
<div class="line"><a id="l00152" name="l00152"></a><span class="lineno">  152</span>                     <span class="stringliteral">&quot;SRTT [&quot;</span> &lt;&lt; round&lt;microseconds&gt;(srtt) &lt;&lt; <span class="stringliteral">&quot;]; &quot;</span></div>
<div class="line"><a id="l00153" name="l00153"></a><span class="lineno">  153</span>                     <span class="stringliteral">&quot;sample period floor [&quot;</span> &lt;&lt; round&lt;microseconds&gt;(sample_period_floor) &lt;&lt; <span class="stringliteral">&quot;].&quot;</span>);</div>
<div class="line"><a id="l00154" name="l00154"></a><span class="lineno">  154</span> </div>
<div class="line"><a id="l00155" name="l00155"></a><span class="lineno">  155</span>      <span class="keywordflow">if</span> (since_sample_start &gt; min_sample_period)</div>
<div class="line"><a id="l00156" name="l00156"></a><span class="lineno">  156</span>      {</div>
<div class="line"><a id="l00157" name="l00157"></a><span class="lineno">  157</span>        <span class="comment">/* Cool, enough time has passed since this sample was started; take a bandwidth sample over</span></div>
<div class="line"><a id="l00158" name="l00158"></a><span class="lineno">  158</span><span class="comment">         * that time period (just bytes/time).  As promised, our units are bytes per Time_unit(1),</span></div>
<div class="line"><a id="l00159" name="l00159"></a><span class="lineno">  159</span><span class="comment">         * so convert from Fine_duration to (the likely less fine) Time_unit before dividing.  We</span></div>
<div class="line"><a id="l00160" name="l00160"></a><span class="lineno">  160</span><span class="comment">         * use ceil() instead of truncation or round() to avoid rounding down to zero and</span></div>
<div class="line"><a id="l00161" name="l00161"></a><span class="lineno">  161</span><span class="comment">         * resulting in division by zero.  (Shouldn&#39;t really happen due to sample_period_floor,</span></div>
<div class="line"><a id="l00162" name="l00162"></a><span class="lineno">  162</span><span class="comment">         * but who knows what they&#39;ve set it to?  Better safe than sorry.) */</span></div>
<div class="line"><a id="l00163" name="l00163"></a><span class="lineno">  163</span> </div>
<div class="line"><a id="l00164" name="l00164"></a><span class="lineno">  164</span>        <span class="keyword">const</span> <a class="code hl_typedef" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a40993b2699c5e8ab69dfd56e57ecdd28">n_bytes_t</a> bytes_per_time_this_sample</div>
<div class="line"><a id="l00165" name="l00165"></a><span class="lineno">  165</span>          = <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a0bf439f5cfe98fb1d4d6d55ae605d278">m_bytes_this_sample</a> / round&lt;Time_unit&gt;(since_sample_start).count();</div>
<div class="line"><a id="l00166" name="l00166"></a><span class="lineno">  166</span> </div>
<div class="line"><a id="l00167" name="l00167"></a><span class="lineno">  167</span>        <span class="comment">// B/W sample computed.  Shove into the filter(s), ultimately updating the main B/W estimate.</span></div>
<div class="line"><a id="l00168" name="l00168"></a><span class="lineno">  168</span> </div>
<div class="line"><a id="l00169" name="l00169"></a><span class="lineno">  169</span>        <span class="keywordflow">if</span> (<a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#ac89711897d0c265eb3b18a748c03d3aa">m_no_samples_yet</a>)</div>
<div class="line"><a id="l00170" name="l00170"></a><span class="lineno">  170</span>        {</div>
<div class="line"><a id="l00171" name="l00171"></a><span class="lineno">  171</span>          <span class="comment">// First sample completed; simply set the estimates to that first sample.</span></div>
<div class="line"><a id="l00172" name="l00172"></a><span class="lineno">  172</span> </div>
<div class="line"><a id="l00173" name="l00173"></a><span class="lineno">  173</span>          <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#ac89711897d0c265eb3b18a748c03d3aa">m_no_samples_yet</a> = <span class="keyword">false</span>;</div>
<div class="line"><a id="l00174" name="l00174"></a><span class="lineno">  174</span> </div>
<div class="line"><a id="l00175" name="l00175"></a><span class="lineno">  175</span>          <a class="code hl_define" href="log_8hpp.html#affcf2e4c496ce3f42adf981669c623b8">FLOW_LOG_TRACE</a>(<span class="stringliteral">&quot;bw_est [&quot;</span> &lt;&lt; sock &lt;&lt; <span class="stringliteral">&quot;] update: first complete sample; bw_est = bw_est_less_smoothed &quot;</span></div>
<div class="line"><a id="l00176" name="l00176"></a><span class="lineno">  176</span>                         <span class="stringliteral">&quot;= [&quot;</span> &lt;&lt; bytes_per_time_this_sample &lt;&lt; <span class="stringliteral">&quot;] bytes per [&quot;</span> &lt;&lt; <a class="code hl_typedef" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a1e5e59588c6683d56866e49e5fd2980e">Time_unit</a>(1) &lt;&lt; <span class="stringliteral">&quot;]&quot;</span></div>
<div class="line"><a id="l00177" name="l00177"></a><span class="lineno">  177</span>                         <span class="stringliteral">&quot;= [&quot;</span> &lt;&lt; util::to_mbit_per_sec&lt;Time_unit&gt;(bytes_per_time_this_sample) &lt;&lt; <span class="stringliteral">&quot; Mbit/s]; &quot;</span></div>
<div class="line"><a id="l00178" name="l00178"></a><span class="lineno">  178</span>                         <span class="stringliteral">&quot;start new sample at 0 bytes.&quot;</span>);</div>
<div class="line"><a id="l00179" name="l00179"></a><span class="lineno">  179</span> </div>
<div class="line"><a id="l00180" name="l00180"></a><span class="lineno">  180</span>          <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#ae6e40f0e24775a09a60dcb7d18242a02">m_bytes_per_time_less_smoothed</a> = bytes_per_time_this_sample;</div>
<div class="line"><a id="l00181" name="l00181"></a><span class="lineno">  181</span>          <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#aee344345b4b4c54a0854bfd23817ef46">m_bytes_per_time_smoothed</a> = <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#ae6e40f0e24775a09a60dcb7d18242a02">m_bytes_per_time_less_smoothed</a>;</div>
<div class="line"><a id="l00182" name="l00182"></a><span class="lineno">  182</span>        }</div>
<div class="line"><a id="l00183" name="l00183"></a><span class="lineno">  183</span>        <span class="keywordflow">else</span></div>
<div class="line"><a id="l00184" name="l00184"></a><span class="lineno">  184</span>        {</div>
<div class="line"><a id="l00185" name="l00185"></a><span class="lineno">  185</span>          <span class="comment">/* 2nd or later sample collected.  Blend the existing value of the filters with the new</span></div>
<div class="line"><a id="l00186" name="l00186"></a><span class="lineno">  186</span><span class="comment">           * sample.</span></div>
<div class="line"><a id="l00187" name="l00187"></a><span class="lineno">  187</span><span class="comment">           *</span></div>
<div class="line"><a id="l00188" name="l00188"></a><span class="lineno">  188</span><span class="comment">           * I am not sure why there are two quantities maintained.  _less_smoothed I get; but</span></div>
<div class="line"><a id="l00189" name="l00189"></a><span class="lineno">  189</span><span class="comment">           * smoothing further to get _smoothed (which is the publicly available B/W estimate) I</span></div>
<div class="line"><a id="l00190" name="l00190"></a><span class="lineno">  190</span><span class="comment">           * don&#39;t.  I didn&#39;t see that in the Westwood/Westwood+ papers, nor is it really explained</span></div>
<div class="line"><a id="l00191" name="l00191"></a><span class="lineno">  191</span><span class="comment">           * in tcp_westwood.c except for one cryptic comment on the westwood-&gt;bw_ns_est struct</span></div>
<div class="line"><a id="l00192" name="l00192"></a><span class="lineno">  192</span><span class="comment">           * member.  Just do it.... */</span></div>
<div class="line"><a id="l00193" name="l00193"></a><span class="lineno">  193</span> </div>
<div class="line"><a id="l00194" name="l00194"></a><span class="lineno">  194</span>          <span class="keyword">const</span> <a class="code hl_typedef" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a40993b2699c5e8ab69dfd56e57ecdd28">n_bytes_t</a> prev_bytes_per_time_less_smoothed = <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#ae6e40f0e24775a09a60dcb7d18242a02">m_bytes_per_time_less_smoothed</a>;</div>
<div class="line"><a id="l00195" name="l00195"></a><span class="lineno">  195</span>          <span class="keyword">const</span> <a class="code hl_typedef" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a40993b2699c5e8ab69dfd56e57ecdd28">n_bytes_t</a> prev_bytes_per_time_smoothed = <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#aee344345b4b4c54a0854bfd23817ef46">m_bytes_per_time_smoothed</a>;</div>
<div class="line"><a id="l00196" name="l00196"></a><span class="lineno">  196</span> </div>
<div class="line"><a id="l00197" name="l00197"></a><span class="lineno">  197</span>          <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#ae6e40f0e24775a09a60dcb7d18242a02">m_bytes_per_time_less_smoothed</a></div>
<div class="line"><a id="l00198" name="l00198"></a><span class="lineno">  198</span>            = <a class="code hl_function" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a2d19118df3aa42de866343893dc75a0a">apply_filter</a>(<a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#ae6e40f0e24775a09a60dcb7d18242a02">m_bytes_per_time_less_smoothed</a>, bytes_per_time_this_sample);</div>
<div class="line"><a id="l00199" name="l00199"></a><span class="lineno">  199</span>          <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#aee344345b4b4c54a0854bfd23817ef46">m_bytes_per_time_smoothed</a></div>
<div class="line"><a id="l00200" name="l00200"></a><span class="lineno">  200</span>            = <a class="code hl_function" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a2d19118df3aa42de866343893dc75a0a">apply_filter</a>(<a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#aee344345b4b4c54a0854bfd23817ef46">m_bytes_per_time_smoothed</a>, <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#ae6e40f0e24775a09a60dcb7d18242a02">m_bytes_per_time_less_smoothed</a>);</div>
<div class="line"><a id="l00201" name="l00201"></a><span class="lineno">  201</span> </div>
<div class="line"><a id="l00202" name="l00202"></a><span class="lineno">  202</span>          <a class="code hl_define" href="log_8hpp.html#affcf2e4c496ce3f42adf981669c623b8">FLOW_LOG_TRACE</a>(<span class="stringliteral">&quot;bw_est [&quot;</span> &lt;&lt; sock &lt;&lt; <span class="stringliteral">&quot;] update: complete sample; &quot;</span></div>
<div class="line"><a id="l00203" name="l00203"></a><span class="lineno">  203</span>                         <span class="stringliteral">&quot;bw_est_less_smoothed &quot;</span></div>
<div class="line"><a id="l00204" name="l00204"></a><span class="lineno">  204</span>                         <span class="stringliteral">&quot;= filter[&quot;</span> &lt;&lt; prev_bytes_per_time_less_smoothed &lt;&lt; <span class="stringliteral">&quot;, &quot;</span> &lt;&lt; bytes_per_time_this_sample &lt;&lt; <span class="stringliteral">&quot;] &quot;</span></div>
<div class="line"><a id="l00205" name="l00205"></a><span class="lineno">  205</span>                         <span class="stringliteral">&quot;= [&quot;</span> &lt;&lt; <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#ae6e40f0e24775a09a60dcb7d18242a02">m_bytes_per_time_less_smoothed</a> &lt;&lt; <span class="stringliteral">&quot;] units &quot;</span></div>
<div class="line"><a id="l00206" name="l00206"></a><span class="lineno">  206</span>                         <span class="stringliteral">&quot;= [&quot;</span> &lt;&lt; util::to_mbit_per_sec&lt;Time_unit&gt;(<a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#ae6e40f0e24775a09a60dcb7d18242a02">m_bytes_per_time_less_smoothed</a>) &lt;&lt; <span class="stringliteral">&quot; Mbit/s]; &quot;</span></div>
<div class="line"><a id="l00207" name="l00207"></a><span class="lineno">  207</span>                         <span class="stringliteral">&quot;bw_est &quot;</span></div>
<div class="line"><a id="l00208" name="l00208"></a><span class="lineno">  208</span>                         <span class="stringliteral">&quot;= filter[&quot;</span> &lt;&lt; prev_bytes_per_time_smoothed &lt;&lt; <span class="stringliteral">&quot;, &quot;</span> &lt;&lt; <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#ae6e40f0e24775a09a60dcb7d18242a02">m_bytes_per_time_less_smoothed</a> &lt;&lt; <span class="stringliteral">&quot;] &quot;</span></div>
<div class="line"><a id="l00209" name="l00209"></a><span class="lineno">  209</span>                         <span class="stringliteral">&quot;= [&quot;</span> &lt;&lt; <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#aee344345b4b4c54a0854bfd23817ef46">m_bytes_per_time_smoothed</a> &lt;&lt; <span class="stringliteral">&quot;] units &quot;</span></div>
<div class="line"><a id="l00210" name="l00210"></a><span class="lineno">  210</span>                         <span class="stringliteral">&quot;= [&quot;</span> &lt;&lt; util::to_mbit_per_sec&lt;Time_unit&gt;(<a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#aee344345b4b4c54a0854bfd23817ef46">m_bytes_per_time_smoothed</a>) &lt;&lt; <span class="stringliteral">&quot; Mbit/s]; &quot;</span></div>
<div class="line"><a id="l00211" name="l00211"></a><span class="lineno">  211</span>                         <span class="stringliteral">&quot;units = bytes per [&quot;</span> &lt;&lt; <a class="code hl_typedef" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a1e5e59588c6683d56866e49e5fd2980e">Time_unit</a>(1) &lt;&lt; <span class="stringliteral">&quot;].&quot;</span>);</div>
<div class="line"><a id="l00212" name="l00212"></a><span class="lineno">  212</span>        } <span class="comment">// if (since_sample_start &gt; min_sample_period)</span></div>
<div class="line"><a id="l00213" name="l00213"></a><span class="lineno">  213</span> </div>
<div class="line"><a id="l00214" name="l00214"></a><span class="lineno">  214</span>        <span class="comment">/* Start new sample.  Note that m_bytes_this_sample is about to get immediately incremented, as explained</span></div>
<div class="line"><a id="l00215" name="l00215"></a><span class="lineno">  215</span><span class="comment">         * at the top. */</span></div>
<div class="line"><a id="l00216" name="l00216"></a><span class="lineno">  216</span> </div>
<div class="line"><a id="l00217" name="l00217"></a><span class="lineno">  217</span>        <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a0bf439f5cfe98fb1d4d6d55ae605d278">m_bytes_this_sample</a> = 0;</div>
<div class="line"><a id="l00218" name="l00218"></a><span class="lineno">  218</span>        <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#ac627f8c9ae6c51c2ea14dd46af4f4150">m_this_sample_start_time</a> = Fine_clock::now();</div>
<div class="line"><a id="l00219" name="l00219"></a><span class="lineno">  219</span>      } <span class="comment">// if (since_sample_start &gt; min_sample_period)</span></div>
<div class="line"><a id="l00220" name="l00220"></a><span class="lineno">  220</span>    } <span class="comment">// if (srtt is valid)</span></div>
<div class="line"><a id="l00221" name="l00221"></a><span class="lineno">  221</span>  } <span class="comment">// if (2nd on_acks() and later)</span></div>
<div class="line"><a id="l00222" name="l00222"></a><span class="lineno">  222</span> </div>
<div class="line"><a id="l00223" name="l00223"></a><span class="lineno">  223</span>  <span class="comment">// As explained earlier, the actual acked bytes contribute to the next sample (if applicable), not preceding one.</span></div>
<div class="line"><a id="l00224" name="l00224"></a><span class="lineno">  224</span> </div>
<div class="line"><a id="l00225" name="l00225"></a><span class="lineno">  225</span>  <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a0bf439f5cfe98fb1d4d6d55ae605d278">m_bytes_this_sample</a> += bytes;</div>
<div class="line"><a id="l00226" name="l00226"></a><span class="lineno">  226</span>  <a class="code hl_define" href="log_8hpp.html#affcf2e4c496ce3f42adf981669c623b8">FLOW_LOG_TRACE</a>(<span class="stringliteral">&quot;bw_est [&quot;</span> &lt;&lt; sock &lt;&lt; <span class="stringliteral">&quot;] update: received acks; sample &quot;</span></div>
<div class="line"><a id="l00227" name="l00227"></a><span class="lineno">  227</span>                 <span class="stringliteral">&quot;total now [&quot;</span> &lt;&lt; sock-&gt;bytes_blocks_str(<span class="keywordtype">size_t</span>(<a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a0bf439f5cfe98fb1d4d6d55ae605d278">m_bytes_this_sample</a>)) &lt;&lt; <span class="stringliteral">&quot;]; &quot;</span></div>
<div class="line"><a id="l00228" name="l00228"></a><span class="lineno">  228</span>                 <span class="stringliteral">&quot;after increment by [&quot;</span> &lt;&lt; sock-&gt;bytes_blocks_str(bytes) &lt;&lt; <span class="stringliteral">&quot;].&quot;</span>);</div>
<div class="line"><a id="l00229" name="l00229"></a><span class="lineno">  229</span>} <span class="comment">// Send_bandwidth_estimator::on_acks()</span></div>
<div class="line"><a id="l00230" name="l00230"></a><span class="lineno">  230</span> </div>
<div class="line"><a id="l00231" name="l00231"></a><span class="lineno"><a class="line" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a2d19118df3aa42de866343893dc75a0a">  231</a></span><a class="code hl_typedef" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a40993b2699c5e8ab69dfd56e57ecdd28">Send_bandwidth_estimator::n_bytes_t</a> <a class="code hl_function" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a2d19118df3aa42de866343893dc75a0a">Send_bandwidth_estimator::apply_filter</a>(<a class="code hl_typedef" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a40993b2699c5e8ab69dfd56e57ecdd28">n_bytes_t</a> prev_val,</div>
<div class="line"><a id="l00232" name="l00232"></a><span class="lineno">  232</span>                                                                           <a class="code hl_typedef" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a40993b2699c5e8ab69dfd56e57ecdd28">n_bytes_t</a> new_sample_val) <span class="comment">// Static.</span></div>
<div class="line"><a id="l00233" name="l00233"></a><span class="lineno">  233</span>{</div>
<div class="line"><a id="l00234" name="l00234"></a><span class="lineno">  234</span>  <span class="comment">// Westwood filter: 7/8 * a + 1/8 * b.</span></div>
<div class="line"><a id="l00235" name="l00235"></a><span class="lineno">  235</span>  <span class="keywordflow">return</span> ((7 * prev_val) + new_sample_val) / 8;</div>
<div class="line"><a id="l00236" name="l00236"></a><span class="lineno">  236</span>} <span class="comment">// Send_bandwidth_estimator::apply_filter()</span></div>
<div class="line"><a id="l00237" name="l00237"></a><span class="lineno">  237</span> </div>
<div class="line"><a id="l00238" name="l00238"></a><span class="lineno"><a class="line" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a8676142f693c447be89b667403fecea1">  238</a></span><a class="code hl_typedef" href="classflow_1_1util_1_1Shared__ptr__alias__holder.html#aef7998db71c60eeb5d1e3d1a97c14886">Peer_socket::Const_ptr</a> <a class="code hl_function" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a8676142f693c447be89b667403fecea1">Send_bandwidth_estimator::socket</a>()<span class="keyword"> const</span></div>
<div class="line"><a id="l00239" name="l00239"></a><span class="lineno">  239</span><span class="keyword"></span>{</div>
<div class="line"><a id="l00240" name="l00240"></a><span class="lineno">  240</span>  <span class="keyword">const</span> <a class="code hl_typedef" href="classflow_1_1util_1_1Shared__ptr__alias__holder.html#aef7998db71c60eeb5d1e3d1a97c14886">Peer_socket::Const_ptr</a> sock = <a class="code hl_variable" href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a380927913e47235684ce014b14371920">m_sock</a>.lock();</div>
<div class="line"><a id="l00241" name="l00241"></a><span class="lineno">  241</span> </div>
<div class="line"><a id="l00242" name="l00242"></a><span class="lineno">  242</span>  <span class="comment">// See comment in same spot in Congestion_control_strategy::socket().</span></div>
<div class="line"><a id="l00243" name="l00243"></a><span class="lineno">  243</span>  assert(sock);</div>
<div class="line"><a id="l00244" name="l00244"></a><span class="lineno">  244</span> </div>
<div class="line"><a id="l00245" name="l00245"></a><span class="lineno">  245</span>  <span class="keywordflow">return</span> sock;</div>
<div class="line"><a id="l00246" name="l00246"></a><span class="lineno">  246</span>}</div>
<div class="line"><a id="l00247" name="l00247"></a><span class="lineno">  247</span> </div>
<div class="line"><a id="l00248" name="l00248"></a><span class="lineno">  248</span>} <span class="comment">// namespace flow::net_flow</span></div>
<div class="line"><a id="l00249" name="l00249"></a><span class="lineno">  249</span> </div>
<div class="ttc" id="abandwidth_8hpp_html"><div class="ttname"><a href="bandwidth_8hpp.html">bandwidth.hpp</a></div></div>
<div class="ttc" id="aclassflow_1_1log_1_1Logger_html"><div class="ttname"><a href="classflow_1_1log_1_1Logger.html">flow::log::Logger</a></div><div class="ttdoc">Interface that the user should implement, passing the implementing Logger into logging classes (Flow'...</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l01280">log.hpp:1284</a></div></div>
<div class="ttc" id="aclassflow_1_1net__flow_1_1Send__bandwidth__estimator_html_a0bf439f5cfe98fb1d4d6d55ae605d278"><div class="ttname"><a href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a0bf439f5cfe98fb1d4d6d55ae605d278">flow::net_flow::Send_bandwidth_estimator::m_bytes_this_sample</a></div><div class="ttdeci">n_bytes_t m_bytes_this_sample</div><div class="ttdoc">The number of bytes acknowledged by receiver since m_this_sample_start_time (the time when the curren...</div><div class="ttdef"><b>Definition:</b> <a href="bandwidth_8hpp_source.html#l00295">bandwidth.hpp:295</a></div></div>
<div class="ttc" id="aclassflow_1_1net__flow_1_1Send__bandwidth__estimator_html_a135f0a46b34063e10abfb16de057cbb3"><div class="ttname"><a href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a135f0a46b34063e10abfb16de057cbb3">flow::net_flow::Send_bandwidth_estimator::bandwidth_bytes_per_time</a></div><div class="ttdeci">n_bytes_t bandwidth_bytes_per_time() const</div><div class="ttdoc">Returns the current estimate of the available outgoing bandwidth per unit time for the containing soc...</div><div class="ttdef"><b>Definition:</b> <a href="bandwidth_8cpp_source.html#l00038">bandwidth.cpp:38</a></div></div>
<div class="ttc" id="aclassflow_1_1net__flow_1_1Send__bandwidth__estimator_html_a1e5e59588c6683d56866e49e5fd2980e"><div class="ttname"><a href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a1e5e59588c6683d56866e49e5fd2980e">flow::net_flow::Send_bandwidth_estimator::Time_unit</a></div><div class="ttdeci">boost::chrono::milliseconds Time_unit</div><div class="ttdoc">The primary time unit over which this class reports bandwidth.</div><div class="ttdef"><b>Definition:</b> <a href="bandwidth_8hpp_source.html#l00167">bandwidth.hpp:167</a></div></div>
<div class="ttc" id="aclassflow_1_1net__flow_1_1Send__bandwidth__estimator_html_a2d19118df3aa42de866343893dc75a0a"><div class="ttname"><a href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a2d19118df3aa42de866343893dc75a0a">flow::net_flow::Send_bandwidth_estimator::apply_filter</a></div><div class="ttdeci">static n_bytes_t apply_filter(n_bytes_t prev_val_per_time, n_bytes_t new_sample_val_per_time)</div><div class="ttdoc">Applies the low-pass filter that takes the given previous result of the filter and blends in the give...</div><div class="ttdef"><b>Definition:</b> <a href="bandwidth_8cpp_source.html#l00231">bandwidth.cpp:231</a></div></div>
<div class="ttc" id="aclassflow_1_1net__flow_1_1Send__bandwidth__estimator_html_a380927913e47235684ce014b14371920"><div class="ttname"><a href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a380927913e47235684ce014b14371920">flow::net_flow::Send_bandwidth_estimator::m_sock</a></div><div class="ttdeci">boost::weak_ptr&lt; Peer_socket::Const_ptr::element_type &gt; m_sock</div><div class="ttdoc">The containing socket (read-only access).</div><div class="ttdef"><b>Definition:</b> <a href="bandwidth_8hpp_source.html#l00269">bandwidth.hpp:269</a></div></div>
<div class="ttc" id="aclassflow_1_1net__flow_1_1Send__bandwidth__estimator_html_a40993b2699c5e8ab69dfd56e57ecdd28"><div class="ttname"><a href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a40993b2699c5e8ab69dfd56e57ecdd28">flow::net_flow::Send_bandwidth_estimator::n_bytes_t</a></div><div class="ttdeci">uint64_t n_bytes_t</div><div class="ttdoc">Type that represents the number of bytes, either as an absolute amount or over some time period.</div><div class="ttdef"><b>Definition:</b> <a href="bandwidth_8hpp_source.html#l00134">bandwidth.hpp:134</a></div></div>
<div class="ttc" id="aclassflow_1_1net__flow_1_1Send__bandwidth__estimator_html_a8676142f693c447be89b667403fecea1"><div class="ttname"><a href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#a8676142f693c447be89b667403fecea1">flow::net_flow::Send_bandwidth_estimator::socket</a></div><div class="ttdeci">Peer_socket::Const_ptr socket() const</div><div class="ttdoc">Utility that returns a handle to the containing Peer_socket.</div><div class="ttdef"><b>Definition:</b> <a href="bandwidth_8cpp_source.html#l00238">bandwidth.cpp:238</a></div></div>
<div class="ttc" id="aclassflow_1_1net__flow_1_1Send__bandwidth__estimator_html_ac627f8c9ae6c51c2ea14dd46af4f4150"><div class="ttname"><a href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#ac627f8c9ae6c51c2ea14dd46af4f4150">flow::net_flow::Send_bandwidth_estimator::m_this_sample_start_time</a></div><div class="ttdeci">Fine_time_pt m_this_sample_start_time</div><div class="ttdoc">The time at which the currently ongoing bandwidth sample began to accumulate.</div><div class="ttdef"><b>Definition:</b> <a href="bandwidth_8hpp_source.html#l00298">bandwidth.hpp:298</a></div></div>
<div class="ttc" id="aclassflow_1_1net__flow_1_1Send__bandwidth__estimator_html_ac89711897d0c265eb3b18a748c03d3aa"><div class="ttname"><a href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#ac89711897d0c265eb3b18a748c03d3aa">flow::net_flow::Send_bandwidth_estimator::m_no_samples_yet</a></div><div class="ttdeci">bool m_no_samples_yet</div><div class="ttdoc">true until a sample has been completed and fed into the filter; false forever thereafter.</div><div class="ttdef"><b>Definition:</b> <a href="bandwidth_8hpp_source.html#l00307">bandwidth.hpp:307</a></div></div>
<div class="ttc" id="aclassflow_1_1net__flow_1_1Send__bandwidth__estimator_html_ad2432d0e20ebfd1b95009e10f10f08be"><div class="ttname"><a href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#ad2432d0e20ebfd1b95009e10f10f08be">flow::net_flow::Send_bandwidth_estimator::Send_bandwidth_estimator</a></div><div class="ttdeci">Send_bandwidth_estimator(log::Logger *logger_ptr, Peer_socket::Const_ptr sock)</div><div class="ttdoc">Constructs object by setting up logging and saving a pointer to the containing Peer_socket.</div><div class="ttdef"><b>Definition:</b> <a href="bandwidth_8cpp_source.html#l00026">bandwidth.cpp:26</a></div></div>
<div class="ttc" id="aclassflow_1_1net__flow_1_1Send__bandwidth__estimator_html_adc8e7ca2c14f74a85beb863c145b97ba"><div class="ttname"><a href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#adc8e7ca2c14f74a85beb863c145b97ba">flow::net_flow::Send_bandwidth_estimator::m_no_acks_yet</a></div><div class="ttdeci">bool m_no_acks_yet</div><div class="ttdoc">true until on_acks() called for the first time; false forever thereafter. Used to begin the sample se...</div><div class="ttdef"><b>Definition:</b> <a href="bandwidth_8hpp_source.html#l00301">bandwidth.hpp:301</a></div></div>
<div class="ttc" id="aclassflow_1_1net__flow_1_1Send__bandwidth__estimator_html_ae6e40f0e24775a09a60dcb7d18242a02"><div class="ttname"><a href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#ae6e40f0e24775a09a60dcb7d18242a02">flow::net_flow::Send_bandwidth_estimator::m_bytes_per_time_less_smoothed</a></div><div class="ttdeci">n_bytes_t m_bytes_per_time_less_smoothed</div><div class="ttdoc">In the same units as m_bytes_per_time_smoothed, the less smoothed bandwidth estimate,...</div><div class="ttdef"><b>Definition:</b> <a href="bandwidth_8hpp_source.html#l00288">bandwidth.hpp:288</a></div></div>
<div class="ttc" id="aclassflow_1_1net__flow_1_1Send__bandwidth__estimator_html_aee344345b4b4c54a0854bfd23817ef46"><div class="ttname"><a href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#aee344345b4b4c54a0854bfd23817ef46">flow::net_flow::Send_bandwidth_estimator::m_bytes_per_time_smoothed</a></div><div class="ttdeci">n_bytes_t m_bytes_per_time_smoothed</div><div class="ttdoc">The current smoothed bandwidth estimate, to be returned by bandwidth_bytes_per_time(),...</div><div class="ttdef"><b>Definition:</b> <a href="bandwidth_8hpp_source.html#l00275">bandwidth.hpp:275</a></div></div>
<div class="ttc" id="aclassflow_1_1net__flow_1_1Send__bandwidth__estimator_html_afe271b3d4c8cb73d06048a41871c795e"><div class="ttname"><a href="classflow_1_1net__flow_1_1Send__bandwidth__estimator.html#afe271b3d4c8cb73d06048a41871c795e">flow::net_flow::Send_bandwidth_estimator::on_acks</a></div><div class="ttdeci">void on_acks(size_t bytes)</div><div class="ttdoc">Informs the bandwidth estimator strategy that 1 or more previously sent packets whose status was In-f...</div><div class="ttdef"><b>Definition:</b> <a href="bandwidth_8cpp_source.html#l00043">bandwidth.cpp:43</a></div></div>
<div class="ttc" id="aclassflow_1_1util_1_1Shared__ptr__alias__holder_html_aef7998db71c60eeb5d1e3d1a97c14886"><div class="ttname"><a href="classflow_1_1util_1_1Shared__ptr__alias__holder.html#aef7998db71c60eeb5d1e3d1a97c14886">flow::util::Shared_ptr_alias_holder&lt; boost::shared_ptr&lt; Peer_socket &gt; &gt;::Const_ptr</a></div><div class="ttdeci">Const_target_ptr Const_ptr</div><div class="ttdoc">Short-hand for ref-counted pointer to immutable values of type Target_type::element_type (a-la T cons...</div><div class="ttdef"><b>Definition:</b> <a href="shared__ptr__alias__holder_8hpp_source.html#l00127">shared_ptr_alias_holder.hpp:127</a></div></div>
<div class="ttc" id="alog_8hpp_html_a626c7dc4d3b4dc0b32a8aac8624d66bc"><div class="ttname"><a href="log_8hpp.html#a626c7dc4d3b4dc0b32a8aac8624d66bc">FLOW_LOG_WARNING</a></div><div class="ttdeci">#define FLOW_LOG_WARNING(ARG_stream_fragment)</div><div class="ttdoc">Logs a WARNING message into flow::log::Logger *get_logger() with flow::log::Component get_log_compone...</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l00152">log.hpp:152</a></div></div>
<div class="ttc" id="alog_8hpp_html_affcf2e4c496ce3f42adf981669c623b8"><div class="ttname"><a href="log_8hpp.html#affcf2e4c496ce3f42adf981669c623b8">FLOW_LOG_TRACE</a></div><div class="ttdeci">#define FLOW_LOG_TRACE(ARG_stream_fragment)</div><div class="ttdoc">Logs a TRACE message into flow::log::Logger *get_logger() with flow::log::Component get_log_component...</div><div class="ttdef"><b>Definition:</b> <a href="log_8hpp_source.html#l00227">log.hpp:227</a></div></div>
<div class="ttc" id="anamespaceflow_1_1net__flow_html"><div class="ttname"><a href="namespaceflow_1_1net__flow.html">flow::net_flow</a></div><div class="ttdoc">Flow module containing the API and implementation of the Flow network protocol, a TCP-inspired stream...</div><div class="ttdef"><b>Definition:</b> <a href="asio_2node_8cpp_source.html#l00024">node.cpp:25</a></div></div>
<div class="ttc" id="anamespaceflow_html_a3938730ab4b89daf13d027a5f620e7ce"><div class="ttname"><a href="namespaceflow.html#a3938730ab4b89daf13d027a5f620e7ce">flow::Flow_log_component</a></div><div class="ttdeci">Flow_log_component</div><div class="ttdoc">The flow::log::Component payload enumeration comprising various log components used by Flow's own int...</div><div class="ttdef"><b>Definition:</b> <a href="common_8hpp_source.html#l00637">common.hpp:638</a></div></div>
<div class="ttc" id="anamespaceflow_html_a48799f1263cdeedec125be51a3db2b79"><div class="ttname"><a href="namespaceflow.html#a48799f1263cdeedec125be51a3db2b79">flow::Fine_duration</a></div><div class="ttdeci">Fine_clock::duration Fine_duration</div><div class="ttdoc">A high-res time duration as computed from two Fine_time_pts.</div><div class="ttdef"><b>Definition:</b> <a href="common_8hpp_source.html#l00416">common.hpp:416</a></div></div>
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